Imported genesis 8 female's vertex groups are not following bone they should be parented to (I'm a noob)
The weight painting is probably off. To fix the teeth find the vertex group with the weight painting for the head first. The bones of the armature have vertex groups with the same name. I don't know if the teeth in your model is a separate object. In my model, it is.
Select the head object, go to Weight Paint mode and search the list of Object Data Properties &gt; Vertex Groups for the head bone. If the head turns red, you probably found the right one. Remember the name of the vertex group. In my example, it's &quot;spine.006&quot;.
Disclaimer: I used Rigify's metarig for a quick pose and the weight painting is very rough and done lazy. But it does the trick for the non-animated pose.

Go to Object Mode and select the teeth object (ignore this step if the teeth are in the head object.) Switch to Edit Mode, select all vertices of the upper teeth and the palate (key L may help). Assign the selected faces to the &quot;spine.006&quot; vertex group. Create a new one if needed. The upper teeth should be in place now.
Repeat the steps for the lower teeth if needed and assign them to the jaw vertex group (&quot;spine.005&quot; in the screenshot). So you can open the mouth properly.

For the glitch at the forehead, you need to check the weight painting in the vertex groups to see what's wrong there. There is probably one vertex assigned to another bone/vertex group or not completely assigned to the head vertex group.